And submarine reference accounts don't come much better than Tata Communications, which operates a global fiber network measuring 240,000km. (See this network map for more details.)

Hon Kit Lam, vice president of the international transmission and IP business at Tata Communications, recently conducted an e-mail Q&A with Light Reading. Here's what he had to say about 400G and related topics:

On what Tata learned from the test:
"We learned from the field test that the next-generation transmission technology 400G is feasible for submarine cables with 6000 km distance on the current dispersion map. This is good news for Tata Communications in the fact that our subsea cables can support the current leading technology of 100G and also the 400G in the future. We also expect that higher spectrum efficiency is possible with this data rate."

On the general outlook for using 400G on subsea cables:
"We regularly look for new technology which could help Tata to expand our subsea cable capacity in next 12-24 months. Although the 400G commercial deployment is still sometime away for long haul subsea, we expect to see wider 400G deployment in metro, terrestrial long-haul or short-haul subsea first. Also, we should see wider deployment of 400G ports on high-density backbone routers between major cities."

On the state of 100G for subsea:
"100G technology has been widely deployed in Tata's network. In fact we have successfully deployed 100G around the globe in all our subsea cable segments. Customers expect a smooth migration path from Nx10G to 100G on the same subsea path without major interruption when they upgrade their core router interface card from 10G to 100G. Our 100G enabled subsea cable network could provide a seamless upgrade path as both technical solution and commercial offering."

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